I guess I am confused about how a MultiAqua works. Is it just a fan coil that uses hot water from the heat pump or is it a mini heat pump that is tied into the ground loop and produces it's own heat?

Posted By engineer on 11/23/2008 2:55 PM

Bill - 29 KBtu from 5 kWh translates to a COP of 1.7. I find that hard to believe given your Envisions and ground temp. Are you sure of those numbers?
Dewayne's rule of thumb works out to a COP of 3.5, perhaps a bit conservative for well-designed systems but useful for ballpark guesstimates.

I looked at the wrong line.  I apologize.  Total HVAC KWH for me today is 4.2 (all in heat mode, includes both units).  Total KBTU transfered is 29 (again combined for both units).  W/BTU is thus 0.14, which is the same as 1.7 KWH/ton (assuming 1 ton is 12,000 BTU).

I'll need some help seeing the relationship to COP.  And perhaps this is best left to another thread, so as to not dilute from this one.

(COP is {(HE + P) / P), where HE is Heat Extracted in BTU/h and P is Power in Watts.  My numbers are total BTU for the day and KWH for the day.)

Best regards,

Bill

Wow this is a great forum. 

Saga continues...

So I wanted to see if both units were running, or if only one was.  It was difficult to tell because they are both on the same stand so one vibrated the other.  I timed the system from 118 degrees up to 123 where the system is satisfied.  It took 8 minutes.  The system took 4 minutes to drop down to 118 where it kicked back on.  I then turned off geo #2.  Same results, ok so that shows me that only one unit was running.  Tried the same with geo number 2.  Temp dropped to 116 degrees and unit 2 kicked on.  I let it run for 10 minutes and the temp never moved.  I kicked geo #1 back on and it took 10 minutes to go from 116 to 123.  This tells me that unit 2 is not functioning.  Contractor will be out this morning to check it all out, but it makes sense now that electricity use went up because both units ran, but only one produced heat. 

THANKS SO FAR TO EVERYONE THIS IS THE BEST SOURCE OF KNOWLEDGE I HAVE COME ACROSS YET!!!

Next question:  I have read that it is more efficient with geothermal to set the temp and leave it consistent.  With the existing oil system i was able to cut oil consumtion in half by using programmable thermostats.   With only being in our house awake for about 5 hours a day would it make any sense to adjust the temps with the existing programmable thermostats while using the geo system?